Scanning image systems generally form a map of some optical characteristic of a surface of interest by moving a focused beam of light in a deliberate and repeatable pattern over the surface and measuring some response. The response is generally time correlated to the position of the scanning beam in order to form a map of the response with respect to its location on the surface. In instances where the features of interest are arranged systematically across the surface (i.e. in an array), it is important to be able to infer the position of the surface represented by each pixel of a surface scan. It is also important to have a high level of confidence that the pixel spacing is uniform within some tolerance dictated by the size of the features being scanned. The moving and optical components that position the scanning spot relative to the surface generally exhibit some systematic position errors. Such errors can be either dynamical (i.e. time dependent) or position dependent. Examples of time dependant errors include those which are a function of the scan profile being performed, the system response of the beam positioning apparatus, or errors due to a non-settled system. Examples of position dependant errors include those which are a function of the static alignment and shape of the scan lens, nonlinear properties of the spot positioning apparatus, or measurements performed at the extreme ends of the scanning system range. Generally, such errors can be categorized as reproducible and non-reproducible deviations from ideal behavior.
While prior systems have attempted to address such concerns, there still exists a need for an improved method and system which will allow systematic errors, regardless of their type or source, to be readily sensed, calibrated, and stored. The resulting compensations to remove the errors can then be applied at a later time to improve the linearity of a scan across the surface of interest.